Many compounds such as the sedative-hypnotics and the minor and major tranquilizers produce relaxation of the skeletal muscles, but these compounds also produce other pharmacological actions which limit their utility as muscle relaxants. Relatively few classes of agents selectively act on the central nervous system to produce muscle relaxation as a primary pharmacological activity.
Succinylcholine chloride is a short acting skeletal muscle relaxant which is of the depolarizing type. Depolarizing skeletal muscle relaxants combine with cholinergic receptor sites on the motor end plate to produce depolarization which may be observed as fasciculations. Subsequent neuromuscular transmission is inhibited as long as an adequate concentration of succinylcholine remain at the receptor site.
More desirable skeletal muscle relaxants are the competitive or nondepolarizing type (curariform) which are easier to control. Nondepolarizing skeletal muscle relaxants antagonize the neurotransmitter action of acetylcholine by competitively inhibiting its binding to, and subsequently activating, cholinergic receptor sites on the motor end plate. This antagonism is inhibited, and neuromuscular block reversed, by acetylcholinesterase inhibitors such as neostigmine, edrophonium, and pyridostigmine. Examples of nondepolarizing skeletal muscle relaxants are pancuronium bromide, atracurium besylate and vecuronium bromide. The activity of these nondepolarizing skeletal muscle relaxants is, however, of intermediate duration and depolarizing skeletal muscle relaxants must be used for activity of short duration.
U.S. Pat. No. 4,200,636, issued to Tuba et al., discloses certain 3-amino-17a-aza-D-homo-5-alpha-androstane quaternary compounds said to be useful as nondepolarizing muscle relaxants having a short activity period.